Why we can’t repair system permissions, and some pitfalls and promise in the new technique of repairing permissions on the Home folder.
MacID
Apple has started recommending users to repair permissions – not generally, but in the Home folder. Here’s my experience, and a tool to make this easier.
We stopped repairing permissions, because of SIP. Now Apple recommends it for a wide range of problems – only this repairs them on your Home folder.
The Eclectic Light Company 